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--                                                                          --

--                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --

--                                                                          --

--    S Y S T E M . V E C T O R S . B O O L E A N _ O P E R A T I O N S     --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--          Copyright (C) 2002-2009, Free Software Foundation, Inc.         --

--                                                                          --

-- GNAT is free software;  you can  redistribute it  and/or modify it under --

-- terms of the  GNU General Public License as published  by the Free Soft- --

-- ware  Foundation;  either version 3,  or (at your option) any later ver- --

-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --

-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --

-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --

--                                                                          --

-- As a special exception under Section 7 of GPL version 3, you are granted --

-- additional permissions described in the GCC Runtime Library Exception,   --

-- version 3.1, as published by the Free Software Foundation.               --

--                                                                          --

-- You should have received a copy of the GNU General Public License and    --

-- a copy of the GCC Runtime Library Exception along with this program;     --

-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --

-- <http://www.gnu.org/licenses/>.                                          --

--                                                                          --

-- GNAT was originally developed  by the GNAT team at  New York University. --

-- Extensive contributions were provided by Ada Core Technologies Inc.      --

--                                                                          --

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--  This package contains functions for runtime operations on boolean vectors

package System.Vectors.Boolean_Operations is

   pragma Pure;

   --  Although in general the boolean operations on arrays of booleans are

   --  identical to operations on arrays of unsigned words of the same size,

   --  for the "not" operator this is not the case as False is typically

   --  represented by 0 and true by 1.

   function "not" (Item : Vectors.Vector) return Vectors.Vector;

   --  The three boolean operations "nand", "nor" and "nxor" are needed

   --  for cases where the compiler moves boolean array operations into

   --  the body of the loop that iterates over the array elements.

   --  Note the following equivalences:

   --    (not X) or  (not Y)  =  not (X and Y)  =  Nand (X, Y)

   --    (not X) and (not Y)  =  not (X or Y)   =  Nor  (X, Y)

   --    (not X) xor (not Y)  =  X xor Y

   --    X       xor (not Y)  =  not (X xor Y)  =  Nxor (X, Y)

   function Nand (Left, Right : Boolean) return Boolean;

   function Nor  (Left, Right : Boolean) return Boolean;

   function Nxor (Left, Right : Boolean) return Boolean;

   function Nand (Left, Right : Vectors.Vector) return Vectors.Vector;

   function Nor (Left, Right : Vectors.Vector) return Vectors.Vector;

   function Nxor (Left, Right : Vectors.Vector) return Vectors.Vector;

   pragma Inline_Always ("not");

   pragma Inline_Always (Nand);

   pragma Inline_Always (Nor);

   pragma Inline_Always (Nxor);

end System.Vectors.Boolean_Operations;